Resin injection systems for use in repairing pipes or conduits and for use in sealing joints formed in communication or electrical cables are generally known. Systems of this type are referred to, for example, in the French patent publication FR 2 702 604 A1 and in the German patent publication DE 100 40 398 A1.
In FR 2 702 604 A1, a resin bag for the resin injection system is illustrated in FIGS. 1 to 3 of the drawings and a non-return valve for the system is illustrated in FIGS. 4 and 5. The non-return valve in this example includes a conventional coil spring that biases a frusto-conically shaped valve body into a closed position seated within a conical recess.
In DE 100 40 398 A1, another example of a non-return valve is illustrated in FIG. 1 of the drawings as part of a resin injection system for sealing or repairing a crack in a gas line, with the non-return valve illustrated in detail in FIGS. 2 and 3. The non-return valve in this example includes curved spring members that are integrally formed with a valve body for biasing the valve body into a closed position seated within a conical recess. Although the non-return valve proposed in DE 100 40 398 A1 has only two parts, i.e. compared with the three-part configuration described in FR 2 702 604 A1, the curved spring members that are integrally formed with the valve body require precise tolerances and render manufacture of the valve quite intricate and therefore relatively costly. Further, the curved spring members may be susceptible to fracture or to release in use, creating problems during resin injection.